This invention relates to turbo machinery rotor construction and, more particularly, to a structure for radially retaining the rotor blades with respect to the rotor disk of a turbo machine.
Turbo machinery such as high performance gas turbine engines have a compressor and turbine, each of which includes one or more annular banks or rows of fixed stator vanes that are positioned between rows of rotatable rotor blades. Each rotor blade is formed with a rotor tip, an airfoil and a dovetail-shaped base or root that is mounted within a mating slot. The dovetail attachment of the turbine blade to the rotor may be defined as a single lobe attachment or a multi-lobe attachment. A dovetail attachment inherently results in an assembly having a measure of radial play to allow axial sliding placement of the turbine blades. The radial play is referred to as radial slop.
Turbine blades with multi-lobe attachments have little radial slop by the inherent nature of the design. The left illustration of FIG. 1 shows a multi-lobe attachment 10 in the running position with the turbine blade loaded radially outwardly. The right illustration of FIG. 1 shows the same blade 10 in the installed position, loaded radially in. As noted, there is a radial position shift delta or slop D m relative to the rotor or hub disk 12.
In contrast, turbine blades with single lobe attachment inherently have a large amount of radial slop. Referring to FIG. 2, on the left a single lobe turbine blade 14 is illustrated in its running position, loaded radially outwardly. The same turbine blade 14 in its installed position, loaded radially inwardly, is illustrated on the right in FIG. 2. As shown, turbine blades with single lobe attachments have significant radial position shift or delta slop D s relative to the rotor disk or hub 16 due to the design. As illustrated in FIG. 3, the radial slop of the turbine blades having single-lobe attachment results in radial mismatch between blades. Radial slop combined with single lobe dovetail creates large platform gaps between blades allowing seals and dampers to fall out. Also, the radial mismatch between adjacent blades causes issues with feather seal slot-alignment and platform damper alignment. Moreover, as illustrated in FIG. 4, the radial slop of the single lobe configuration permits blades to rock when not seated on the pressure face.
The invention provides for a simple and inexpensive fabrication to provide radial position retention to minimize the problems associated with single lobe attachment radial slop.
Thus, the invention may be embodied in a blade retention system for a rotating machine comprising: a hub having a plurality of shaped, generally axially extending, radially open slots at circumferentially spaced positions about the hub; a blade having complimentary shaped base portion axially received in a said slot and extending radially outwardly therefrom; and a radial retainer for spacing a radially inner end of said blade from a bottom surface of said slot, said retainer including a main body and a resilient component for resiliently urging the blade radially outwardly of said slot.
In an exemplary embodiment, the invention is embodied in a radial retainer for spacing a radially inner end of a turbine blade from a bottom surface of a respective slot, comprising: a generally planer main body including a base portion and a frame portion; and a resilient component, said resilient component being coupled to and extending from said base portion.
The invention may also be embodied in a method of radially retaining a turbine blade in a turbine blade slot, comprising: providing a hub having a plurality of shaped, generally axially extending, radially open slots at circumferentially spaced positions about the hub; engaging a blade having complimentary shaped base portion with a said slot so that said base of said blade is axially slidably disposed in said slot and said blade extends radially outwardly therefrom; and inserting a radial retainer between a radially inner end of said blade and a bottom surface of said slot, said radial retainer including a main body and a resilient component for resiliently urging the blade radially outwardly of said slot.